Was it a new Barack Obama who flew home from Tucson in the early hours of yesterday or the old one he had lost sight of?

In 33 minutes on Wednesday night he had reminded Americans of what used to be the essence of his appeal: his conviction that politics – and leadership – should be about uniting not dividing.

Moments of great tragedy become moments of opportunity for every president. But the days since the shootings in Tucson last weekend arguably demanded Mr Obama's touch especially. While America was stunned by the rampage that left six dead and 13 wounded, including the Congresswoman Gabrielle Giffords, it was also plunged into a new spiral of ideological eye-gouging. Did the right cause this? Did Sarah Palin?

Before he became President, Mr Obama proclaimed there was no red America or blue America, referring to the colours of the parties, but only a United States of America. And so Mr Obama, addressing a crowd of 14,000 in a University of Arizona basketball arena, said exactly what you would hope. Rise above this, he said. Use it to make ourselves and our country better.

"If this tragedy prompts reflection and debate, as it should, let's make sure it's worthy of those we have lost," Mr Obama said. "Let's make sure it's not on the usual plane of politics and point-scoring and pettiness that drifts away with the next news cycle." He was at his most effective evoking the life of nine-year-old Christina Green whose burial was due yesterday afternoon. This morning will see the funeral of John Roll, the most senior federal judge in Arizona until he too was killed.

The little girl, Mr Obama noted, had shown an early interest in democracy and politics, joining her school student council and asking to go along to Saturday's event to see a Congressperson in the flesh. "I want to live up to her expectations," the President told the crowd and the national TV audience. "I want our democracy to be as good as Christina imagined it. I want America to be as good as she imagined it."

Several times at the memorial event the mostly youthful audience was more anxious to yell appreciation than share in grieving.

They whistled for their President and roared for the heroes of the shooting tragedy. And no one drew their gratitude or admiration more than the 20-year-old Daniel Hernandez, a political science student seated on the right of Mr Obama.

An unpaid intern in the Tucson constituency office of Ms Giffords, he had rushed forward in the hail of bullets to apply pressure to the head wounds of the Congresswoman and ensured that she was able to breathe. He told the Congresswoman to squeeze his hand to help her cope with her great pain. With his courage, he may just have saved her life.

The country may not heed President Obama's message, of course. Ms Palin had earlier in the day demonstrated just how powerful the pull into point-scoring can be with a video cameo that saw her lashing out at those who had sought to connect her sometimes incendiary rhetoric to the shooting. They were guilty of "blood libel", she said.

The contrast between Ms Palin and Mr Obama was jarring.

"Rather than pointing fingers or assigning blame, let us use this occasion to expand our moral imaginations," the President said, "to listen to each other more carefully, to sharpen our instincts for empathy, and remind ourselves of all the ways our hopes and dreams are bound together." Ms Palin will have delighted her core constituents. But the higher ground was surely Mr Obama's.

"I wouldn't underestimate how this is going to affect the perception of the President," noted Charles Krauthammer, the normally hostile columnist on The Washington Post.

Steve Lombardo, who does polling for the Republicans, told Politico: "It was supposed to be simply a chance to make a good speech, but it may be more than that. It may be a time when we look back and say that he remade himself tonight into the President we thought he could be."

The road back for Tucson may be longer. As residents begin to bury those killed, they are also learning more about the suspect, 22-year-old Jared Loughner, and behaviour that spoke so loudly of a troubled soul. New police documents revealed a previous outburst about attaching bombs to babies.

Speech extracts

"Rather than pointing fingers or assigning blame, let us use this occasion to expand our moral imaginations, to listen to each other more carefully, to sharpen our instincts for empathy, and remind ourselves of all the ways our hopes and dreams are bound together."

"If this tragedy prompts reflection and debate, as it should, let's make sure it's worthy of those we have lost. Let's make sure it's not on the usual plane of politics and point-scoring and pettiness that drifts away with the next news cycle."

"I want our democracy to be as good as Christina imagined it. I want America to be as good as she imagined it... If there are rain puddles in Heaven, she is jumping in them today. And here on this Earth, we place our hands over our hearts, and we commit ourselves as Americans to forging a country that is forever worthy of her gentle, happy spirit."